In order to increase drainage efficiency of a tire in the rain and thereby to exhibit excellent hydroplaning performance, it is effective to dispose a circumferential groove on a wheel tread part of a tread.
In a pneumatic radial tire in this case, the wheel tread part of the tread is constituted of at least one circumferential groove formed in a circumferential direction and a plurality of transverse grooves formed at proper intervals in a width direction so as to intersect the circumferential groove which divide the wheel tread part into a plurality of block. The circumferential groove functions to increase drainage efficiency of the tire in the rain.
However, the conventional pneumatic radial tire has a problem that the disposition of the circumferential groove generates a dead zone at the start of changing a steering angle, and especially there is a fear of slight deterioration of a response of handling performance during lane changing.
Incidentally, the followings are available as prior art document information related to this application:
Japanese Patent Application Laid-Open No. 2000-185526
Japanese Patent Application Laid-open No. Hei 9-109613